In previous studies we have shown that low levels of renal sympathetic nerve activity which do not themselves alter renal blood flow, urinary sodium excretion, or renin release augment the renin secretion responses to suprarenal aortic constriction and to furosemide administration. In the coming year, the role of alpha and of beta adrenergic receptors in mediating this modulating influence of the renal nerves on renin secretion will be investigated. The responses of innervated and contralateral denervated kidneys to aortic constriction will be determined before and following the administration of the beta blocker, metoprolol, and before and after the administration of the alpha blocker, phentolamine. The responses of innervated and contralateral denervated kidneys to furosemide and to aortic constriction will also be determined before and after blockade of prostaglandin synthesis with indomethacin to determine if prostaglandins play a role in the modulating influence of the renal nerves on renin secretion mediated by non-neural mechanisms.